*"This royal throne of kings, this sceptred isle, This earth of majesty,
this seat of Mars, This other Eden, demi-paradise, This fortress built by
Nature for herself Against infection and the hand of war, This this little
world, This precious stone set in the silver sea, Which serves it in the
office of a wall Or as a moat defensive to a house, Against the envy of
less happier lands,-- This blessed plot, this earth, this realm, this*

*SOUTHWORTH PLANETARIUM"*207-780-4249       www.usm.maine.edu/planet
70 Falmouth Street  Portland, Maine 04103
43.6667° N,                    70.2667° W
Founded January 1970



*THE DAILY ASTRONOMER*

*Monday, May 23, 2016*
*Apollo Pandora *

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We've added a new -and small- feature to the DA
Find it after the footnotes.
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When assailed by the tumults of this unquiet Earth, one often seeks to
restore a sense of normalcy to one's life.    In this vein, we return today
to Pandora's Jar: the vessel stuffed to the brim with astronomical
questions inscribed on parchment paper.  What with all our adventures of
late, we haven't had an opportunity to visit Pandora within the last week.
      Sometimes, we select a question at random, as we prefer to let the
Universe choose for us. (In other words, we're just feeling too darn lazy
to examine the parchment pieces individually.)  Other times, such as now,
we organize them by topic.      So, today, our two Pandora parchments
pertain to what astronauts left on the moon, hence the title "Apollo
Pandora."



*"I have always been fascinated with the Apollo moon mission.  I've often
wondered if can we see the Lunar rover with a telescope.  Can we?"
     -Seth P,  South Portland*

Greetings!
Unfortunately, not even the most powerful telescopes will allow us to see
such small objects on the moon as the Lunar Roving Vehicle.   The LRV is
still parked on the surface, as shown by the LRO (Lunar Reconnaissance
Orbiter) below.  However, the problem is in the resolution.  This vehicle
cannot be distinguished against the moon's surface.      Remember that we
are nearly a quarter of a million miles from the moon!   Simply,  we are
too far away.

Now, to understand why distance matters, we will include some numbers.
First, a telescope's resolution depends on its effective diameter (or the
diameter of its lens, a value known as "aperture.").   We can approximate a
telescope's resolution power with the formula  R = 11.6/D, where D is the
diameter in cm and R is the resolution in arc-seconds.*        The Hubble
Space Telescope uses an objective mirrors with a diameter of 240 cm, so its
resolution power is 0.05 arc-seconds.   By this calculation, we have
determined that the Hubble Space Telescope can only resolve objects with
resolutions greater than 0.05 arc-seconds.**
We know that the lunar rover is about 4 meters across and its angular
measure from Earth's distance is a vanishingly small  0.002 arc-seconds!
Not even the Hubble Space Telescope can observe the lunar rover.

We know it is still there, however, even if it is out of our sight.



*​This 2011 image of the Apollo 17 landing site captured by NASA's  Lunar
Reconnaissance Orbiter.*

*The LRV, Lunar Roving Vehicle, is seen at the right hand edge of the*

*image.     As this orbiter was far closer to the moon than
Earth-observers, it was *
*able to resolve the LRV against the lunar surface. (Image courtesy of
NASA)*




*"Is it true that the American flag left on the moon is now white?"*

*-Miriam S,  Casco*

Yes!
The red, white and blue is now, well, just white.
When the astronauts planted the stars and stripes onto the lunar surface,
they did so with the knowledge that they were exposing old glory an
onslaught of unfiltered solar radiation.  While Earth is shielded by an
atmosphere, the moon is not.    The harsh star light strikes the moon
without being softened by any intervening gases.   Consequently, it has
completely bleached the American flag!  Were we to visit the old landing
sites today, we would see still tracks from the lunar rover, astronaut foot
prints that look as though the astronauts left five minutes ago, and stark
white flags.       It looks as though the astronauts came to conquer the
moon, thought better of it upon arrival and then left a flag of surrender
behind.    And that explains, of course, why they've never returned.



*Apollo 17 astronaut Eugene Cernan, the last human to walk on the moon, *

*poses with an American flag.  Even though the flag's colors are
distinctive in this*

*photo, the flag is now most assuredly white, as the Sun's harsh radiation
has*
*completely bleached it.   (Image courtesy of NASA.)*
​


**There's always room for arc-seconds.   A circle contains 360 degrees.  A
degree can be sub-divided into 60 arc-minutes.  An arc-minute can, itself,
be divided into sixty equal parts called "arc-seconds."     To give one an
intuitive notion about arc-seconds, an arc-second is equal to the width of
a dime at a distance of 1.25 miles!    *

***Life can be a mess.   This is a theoretical lower limit.  Generally, due
to complicating factors, the Hubble's actual limiting resolution is about
twice its lowest limit, or about 0.1 arc-second. *


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FROM THE CATACOMBS OF INFINITE KNOWLEDGE:
Abe Silverstein, Director of Space Flight Development, proposed the name
"Apollo"
for NASA's moon program.  NASA approved the name in 1960 and the rest is
history.
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